The present invention relates to a new method of producing a phosphinyl-carboxylic acid derivative (or phosphinic acid derivative) which can be used as a flame-retardant for polyester or a bi-functional reactive flame-retardant, or an intermediate thereof.
Conventionally, a phosphinyl-carboxylic acid derivative has been produced by the following reaction set forth in Zhural Obsh. khim. 37, 455-460, 1967 (C.A. 67, 32744 v). ##STR3##
In this method using no catalyst, however, the reaction takes a long period of time (about 15 days at room temperature) and the yield is as low as about 71%. Thus, this method is not suitable for industrial application.
To overcome such defects, U.S. Pat. No. 4,081,463 has proposed the use of an excessive amount of acrylic acid to improve the yield. However, such a method is disadvantageous in view of effluent disposal due to excessive use of acrylic acid.